package org.wustrive.java.common.digest;

import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

public class RSACoder {
	 /**
     * 非对称加密密钥算法
     */
    public static final String KEY_ALGORITHM = "RSA";

    /**
     * 公钥
     */
    private static final String PUBLIC_KEY = "RSAPublicKey" ;

    /**
     * 私钥
     */
    private static final String PRIVATE_KEY = "RSAPrivateKey" ;

    /**
     * RSA密钥长度
     * 默认1024位，
     * 密钥长度必须是64的倍数，
     * 范围在512至65536位之间。
     */
    private static final int KEY_SIZE = 512;

    /**
     * 私钥解密
     *
     * @param data
     *            待解密数据
     * @param key
     *            私钥
     * @return byte[] 解密数据
     * @throws Exception
     */
    public static byte [] decryptByPrivateKey(byte[] data, byte[] key)
              throws Exception {

          // 取得私钥
         PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(key);

         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

          // 生成私钥
         PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

          // 对数据解密
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

         cipher.init(Cipher. DECRYPT_MODE, privateKey);

          return cipher.doFinal(data);
    }

    /**
     * 公钥解密
     *
     * @param data
     *            待解密数据
     * @param key
     *            公钥
     * @return byte[] 解密数据
     * @throws Exception
     */
    public static byte [] decryptByPublicKey(byte[] data, byte[] key)
              throws Exception {

          // 取得公钥
         X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);

         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

          // 生成公钥
         PublicKey publicKey = keyFactory.generatePublic(x509KeySpec);

          // 对数据解密
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

         cipher.init(Cipher. DECRYPT_MODE, publicKey);

          return cipher.doFinal(data);
    }

    /**
     * 公钥加密
     *
     * @param data
     *            待加密数据
     * @param key
     *            公钥
     * @return byte[] 加密数据
     * @throws Exception
     */
    public static byte [] encryptByPublicKey(byte[] data, byte[] key)
              throws Exception {

          // 取得公钥
         X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);

         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

         PublicKey publicKey = keyFactory.generatePublic(x509KeySpec);

          // 对数据加密
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

         cipher.init(Cipher. ENCRYPT_MODE, publicKey);

          return cipher.doFinal(data);
    }

    /**
     * 私钥加密
     *
     * @param data
     *            待加密数据
     * @param key
     *            私钥
     * @return byte[] 加密数据
     * @throws Exception
     */
    public static byte [] encryptByPrivateKey(byte[] data, byte[] key)
              throws Exception {

          // 取得私钥
         PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(key);

         KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);

          // 生成私钥
         PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec);

          // 对数据加密
         Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());

         cipher.init(Cipher. ENCRYPT_MODE, privateKey);

          return cipher.doFinal(data);
    }

    /**
     * 取得私钥
     *
     * @param keyMap
     *            密钥Map
     * @return byte[] 私钥
     * @throws Exception
     */
    public static byte [] getPrivateKey(Map<String, Object> keyMap)
              throws Exception {

         Key key = (Key) keyMap.get( PRIVATE_KEY);

          return key.getEncoded();
    }

    /**
     * 取得公钥
     *
     * @param keyMap
     *            密钥Map
     * @return byte[] 公钥
     * @throws Exception
     */
    public static byte [] getPublicKey(Map<String, Object> keyMap)
              throws Exception {

         Key key = (Key) keyMap.get( PUBLIC_KEY);

          return key.getEncoded();
    }

    /**
     * 初始化密钥
     *
     * @return Map 密钥Map
     * @throws Exception
     */
    public static Map<String, Object> initKey() throws Exception {

          // 实例化密钥对生成器
         KeyPairGenerator keyPairGen = KeyPairGenerator
                 . getInstance(KEY_ALGORITHM);

          // 初始化密钥对生成器
         keyPairGen.initialize( KEY_SIZE);

          // 生成密钥对
         KeyPair keyPair = keyPairGen.generateKeyPair();

          // 公钥
         RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();

          // 私钥
         RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

          // 封装密钥
         Map<String, Object> keyMap = new HashMap<String, Object>(2);

         keyMap.put( PUBLIC_KEY, publicKey);
         keyMap.put( PRIVATE_KEY, privateKey);

          return keyMap;
    }

}
